(nin-juh up) verb. The act of tying a black t-shirt to ones face and doint subversive activities. Usually used when stealing cigarettes or blowing up peoples cars.
Johnny Twobags - Man, Ame has a pack of Newports, but shes asleep and I'd have to crawl over her.
Mr. Dopey - You'd better ninja up and do that shit
*Johnny Twobags ties his shirt up and backflips off the ceiling.
The act of solving any and all problems through the use of voilence and smoke bombs.
Stop crying, ninja up, and hit him or her in the neck with a throwing star."This sentence can be used for any situation."